Activating product

ABSTRACT

A surface activating material in the form of a sheet wherein a plurality of fine, flexible non-conductive projections, such as bristles, protrude substantially uniformly from a porous, extremely open, fluid-entrapping and circulating matrix and wherein fine, non-conductive hard particles are affixed to such projections and to the surface of the open matrix from which they protrude.

Sept. 11, 1973 s l H 3,758,393

ACTIVATI NG PRODUCT Filed March '19, 1971 V TOR HUGH E. MITH ATTORNEY United States Patent 3,758,393 ACTIVATING PRODUCT Hugh E. Smith, Troy, N.Y., assignor to Norton Company, Troy, N.Y. Filed Mar. 19, 1971, Ser. No. 126,193 Int. Cl. B01k 3/00; C23b 5/72; D04h 1/00 US. Cl. 204-279 4 Claims ABSTRACT OF THE DISCLOSURE A surface activating material in the form of a sheet wherein a plurality of fine, flexible non-conductive projections, such as bristles, protrude substantially uniformly from a porous, extremely open, fluid-entrapping and circulating matrix and wherein fine, non-conductive hard particles are affixed to such projections and to the surface of the open matrix from which they protrude.

FIELD OF THE INVENTION The present product is specifically designed for use with the electrodeposition process described and claimed in the copending application, Ser. No. 34,500 of Steve Eisner, filed 'May 4, 1970, now US. Pat. No. 3,619,401. As related therein, the use of products of the general type of those of the present invention to lightly and repetitively contact a surface (an electrode or electrodeposit surface in the cited application) results in an activation of the surface making possible speeds of electrodeposition far above those indicated as achievable by the prior art.

The present invention is designed for use in a process in which the current density is high compared with that of conventional processes and in which the surface of the deposit is repetitively contacted at extremely short time intervals by what is termed herein as dynamically hard particles. By this term is meant that the combination of the hardness of the particles, the contact pressure of the particles on the surface of the electrodeposit and the speed at which such particles are moving relative to the electrodeposit surface is such as to produce an action on such surface sufiicient to mechanically activate the surface. "Activating the surface of the electrodeposit as the term is used herein requires the generation of new surface defect sites through mechanically distorting the crystal lattice of the metal deposited. It is believed that the mechanism is rather complex and consists of several actions taking place essentially simultaneously. First, there is the new surface defect site generation resulting from distortion of the crystal lattice structure as mentioned above. This provides growth sites for many more asperities than would be the case absent this mechanical distortion. Additionally, any dominant asperities already formed are cut off or bent over and crushed by the dynamically hard particle contact. These two actions result in substantial elimination of the current robbing which takes place at the asperities formed in normal plating and is believed to be one of the major contributing factors of the ability to maintain high current densities for substantial periods of time while maintaining acceptable deposits with this process. Further, the action of the activating medium is believed to result in the removal or substantial diminution of the stagnant polarization layer overlying the electrodeposit surface and to maintain a high concentration of metal ions adjacent such surface due to the pumping action of the activating medium which carries a supply of fresh electrolyte across the electrodeposit surface at a high flow rate.

The material utilized in this process consists essentially of a two-component structure, one component comprising a surface distributing or activating medium having the characteristics of providing a plurality of small, dynamically hard, relatively inflexible particles held in substantially fixed, spaced relationship to one another, and generally vertical to the surface being activated, on a plurality of flexible, small diameter non-conductive projections ex tending a relatively short distance from the surface of the second component. This second component has the characteristics of being able to entrap and carry a high volume of liquid within the interstices thereof and preferably consists of an extremly high void volume non-woven material as is described in detail below. For convenience in reference, this is hereinafter sometimes referred to as a fiuid-entrapping and circulating layer. Further, relative motion is provided during the deposition operation between the surface receiving the deposit and the activating medium of the present invention. The spacing of the particles and the speed of relative movement is such that the deposited metal surface above any given point on the cathode surface is contacted or influenced by a particle at extremely short time intervals, e.g. intervals in the range of 6.1 X 10- to 3.8 X10 seconds. Fresh electrolyte is supplied to the zones of activated metal deposit at a high rate through entrapment by the porous component of the activating medium of the present invention.

DESCRIPTION OF THE PRIOR ART Abrasive products have historically been so constructed as to maximize the cut or abrading potential of the specific construction concerned. In the present instance stock removal is not the object. Spaced particles are essential, but they must be so characterized in the product as to provide a controlled abrasion in use. The closest type of activating device to that described herein, we believe, has been the brush or cloth used in so-called brush-plating. This, however, does not contain the spaced particles required in the present structure. Many abrading materials have heretofore been described utilizing abrasive bristles-either with the abrasive applied externally to the pile fabric type bristles, e.g., U.S. 1,850,413; 2,347,244; 2,996,368; or with the abrasive incorporated in the bristle during its formation, e.g. US. Pat. 2,920,947. However, these are all unsuitable per se in the present invention as will be apparent from the detailed description below.

SUMMARY The activating material of the present invention is a flexible structure having a plurality of fine non-conductive bristles or the like protruding from the surface of a compressible, flexible, porous, open, non-conductive, high void volume fluid-entrapping and circulating substrate. The surfaces of the bristles and to some extent the surface through which they protrude carries a plurality of spaced hard particles afi'ixed thereto. Preferably a third component of the structure is an underlying porous supporting or reinforcing web which affords strength to the structure and which provides a convenient anchorage for the inner ed of the bristles. A modification of the invention eliminates the porous supporting web and substitutes an inert metal anode sheet therefor.

DRAWINGS FIG. 1 shows a cross section of a piece of flexible sheeting representing one embodiment of the present invention.

FIG. 2 illustrates schematically the use of the activating material of the present invention in an electroplating process.

FIG. 3 illustrates a cross-section of another embodiment of the invention.

3 DESCRIPTION OF PREFERRED EMBODIMENTS The material of the present invention permits the development of a relatively uniform product in terms of the spacing of the hard particles carried thereby in contrast to the relatively non-uniform product which results when a non-woven particle-supporting substrate is used. The preferred starting material is a pile fabric formed by any of the conventional methods wherein a plurality of fibers extend substantially vertically from the remaining uncut fibers of the base fabric. The pile fabric can also be formed by flocking, i.e., deposition of the fibers onto an adhesively coated substrate and anchorage of such fibers by one end to such substrate. Additionally, standard brush-forming techniques can be utilized for some forms of the invention. The requisite is the provision of a plurality of spaced, vertically upstanding non-conductive fibers or filaments extending relatively uniformly from a temporary or permanent base member. A variation of the invention wherein the fibers are vertically anchored to a non-porous lead or other inert, conductive metal backing is also contemplated. The fibers are selected to be chemically inert to the normal electrolyte solution used in electrodeposition which is the preferred field of use of this material. Selection of the particular material of which the fiber is composed will be dependent upon its ultimate end use and is well within the scope of one skilled in the art. Typical preferred fibrous materials are polyester fibers, e.g. Dacron. Other acid-resistant fibers such as acrylic, modacrylic, polyolefine, flurocarbon and glass can be used if desired. Fiber diameters may vary, e.g. from 0.001" to 0.05", but preferably fibers having average diameters of from 0.00 to 0.03" are used.

Preferably the fibers are at least 43" in length and may range up to as much as one inch or more. The preferred length range is from A3 to A". The fibers are preferably trimmed to provide a uniform distance from the base to the tips thereof.

Once the fibers are provided in a vertically-oriented relationship to the supporting base, a non-conductive, compressible high void volume, open, porous material is pressed down over the fibers so that the fibers penetrate and extend therethrough. The preferred material is a high loft, non-woven web formed of the types of fibrous mate rials identified above and formed on a Rando-Webber type non-woven machine. A typical web of this character is described in US. Pat. 3,020,139. However, in the present instance, the fibrous mat from the Rando-Webber, while it can be used without any binder, preferably has a single polyurethane type binder which is resistant to the electrolyte solutions with which it will generally come in contact. The web should be of a thickness that will permit it to be compressed only slightly and still allow the vertical fibers upon which it is pressed to extend therethrough. Other materials such as reticulated foam, extremely-open sponge, etc., may be used in place of the non-woven if desired.

The vertical fibers generally need extend only a very short distance, e.g., & above the surface of the porous layer. In any event, the fibers should not extend more than about from the porous layer surface.

Following the appliction of the preferred non-woven material to the vertical fiber surface and compaction to the degree required to obtain extension of the vertical fibers through such non-woven, a plurality of small, nonconductive particles are applied to the protruding portion of the vertical fibers and usually, because of the practical difficulty in avoiding it, to the surface of the nonwoven adjacent such protruding vertical fibers. This application of particles may be done in several ways. Since the particles must be fixed in position on the fibers in the end product, an adhesive binder is also required. The particles and binder can be applied together in the form of a slurry, roll coated or sprayed onto the surface, or the material may be inverted and surface-dipped only in an adhesive bath. This latter method is preferred since the adhesive will primarily contact the protruding bristles and a subsequent application by gravity dropping of particles onto the surface results in a predominance of adhesion of particles only to the protruding bristles. The particles may be any of a variety of non-conductive materials such as cured resin, abrasive grain or the like, while the pre ferred particles have been found to be silicon carbide abrasive grit. These particles should not exceed 320 grit size and may go down to the extremely fine micron sizes used in the lapidary trade. Usually grit 400-600 silicon carbide is used.

The application of binder and particles to the structure also serves the purpose of anchoring the non-woven into fixed relationship with the rest of the structure. In some instances it may be desirable to adhere the non woven to the bristles or substrate separately but generally this is not necessary. If desired, once the non-woven is anchored to the fibers, the base which initially supported the fibers can be removed. Generally this is unnecessary, particularly if such base is itself highly open and porous.

Referring now to the drawings, FIG. 1 shows a typical material of the present invention. A pile fabric 10 consisting of a porous, woven base portion 11 and a plurality of cut, vertically-upstanding fibers 12 is provided. Embedded in the vertical fibers 12 is an open non-woven web member 13. The vertical fibers 12 extend above the nonwoven 13 a finite distance (X). This distance is not critical in terms of absolute uniformity and will vary slightly across the product as illustrated due to the uneven web 13 and its varying degrees of compression. Applied to the protruding tips 14 of fibers 12 are a plurality of adhesively-secured hard particles 15. It will be seen that the distance from the tips 14 to the bottom of the support or base portion 11 is substantially uniform throughout.

FIG. 2 illustrates the use of the material of FIG. '1 in a typical application. Here a metal substrate 20, electrically connected to a source of negative potential is disposed in a bath of electrolyte 21. As shown, the substrate is moving from left to right through the bath as indicated by the arrow. Positioned above and in contact with the metal substrate 20 is a rotating disc 22 of the material of the present invention. This is shown mounted on a rotating inert anode disc 23 driven by a shaft 24 and motor 25. Shaft 24 is connected to a ground or to a source of positive potential. As the disc 22 rotates, it activates the surface of the substrate 20 with which it is in contact and an electrodeposit or plate 26 is formed on such surface. The disc also activates this plate and causes extremely rapid build-up of the metal plate as is described and claimed in the aforementioned Eisner application, Ser. No. 34,500. As shown, the compressibility of the material of the disc 22 permits it to conform to the varying thickness of the plate 26.

FIG. 3 illustrates a modified form of the present invention wherein a plurality of bristles 30 are afiixed vertically to an inert lead base member 31. Electrically conductive adhesive 32 is used to adhere the base of bristles 30 to the base member 31. Again, a non-Woven web 33 is disposed within the bristles 30 so that only the tips 34 thereof extend above the non-woven 33. A plurality of spaced hard particles 35 are adhesively secured to the tips 34 of bristles 30.

Materials of the present invention find their preferred use in the electrodeposition process described in the aforementioned Eisner U.S. Pat. No. 3,619,401, but may be used for surface activation in other electrochemical or non-electrochemical processes with good success.

What is claimed is:

1. Surface activating material comprising a compressible, flexible, porous, open, non-conductive, high void volume fiuid-entrapping and circulating layer; a plurality of flexible non-conductive fibers extending through said fiuid-entrapping and circulating layer with one end of each of said plurality of fibers protruding above the upper surface of said fluid-entrapping and circulating layer; and a plurality of small, hard, non-conductive particles adhesively secured to said protruding ends of said fibers and to said upper surface of said fiuid-entrapping and circulating layer.

2. A surface activating material as in claim 1 wherein the other end of each of said plurality of fibers is secured to a base member at least coextensive with said fluid-entrapping and circulating layer.

3. A surface activating material as in claim 2 wherein said base member is a flexible, porous web.

4. A surface activating material as in claim 2 wherein said base member is an inert, electrically-conductive metal structure.

References Cited UNITED STATES PATENTS JOHN H. MACK, Primary Examiner D. R. VALENTINE, Assistant Examiner U.S. Cl. X.R.

51294, 295, 400, 404; 15672; 16166, 67, 164; 2O4DIG. 10, 224 R 

